rs139327086

Positions:

• chr2-165874774-C-A
• chr2-165874774-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_024753.5(TTC21B):​c.3932G>T​(p.Arg1311Leu) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,334 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R1311G) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TTC21B NM_024753.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 5.84

Genes affected

TTC21B (HGNC:25660): (tetratricopeptide repeat domain 21B) This gene encodes a member of TTC21 family, containing several tetratricopeptide repeat (TPR) domains. This protein is localized to the cilium axoneme, and may play a role in retrograde intraflagellar transport in cilia. Mutations in this gene are associated with various ciliopathies, nephronophthisis 12, and asphyxiating thoracic dystrophy 4. [provided by RefSeq, Oct 2011]

ACMG classification

Verdict is Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.81

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTC21B	NM_024753.5	c.3932G>T	p.Arg1311Leu	missense_variant	29/29	ENST00000243344.8	NP_079029.3
TTC21B	XM_047445870.1	c.3278G>T	p.Arg1093Leu	missense_variant	25/25		XP_047301826.1
TTC21B	XM_011511871.4	c.3182G>T	p.Arg1061Leu	missense_variant	24/24		XP_011510173.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTC21B	ENST00000243344.8	c.3932G>T	p.Arg1311Leu	missense_variant	29/29	1	NM_024753.5	ENSP00000243344	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461334 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 727004

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Jeune thoracic dystrophy;C0687120:Nephronophthisis Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 23, 2020

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with TTC21B-related conditions. This variant is not present in population databases (ExAC no frequency). This sequence change replaces arginine with leucine at codon 1311 of the TTC21B protein (p.Arg1311Leu). The arginine residue is highly conserved and there is a moderate physicochemical difference between arginine and leucine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.45
BayesDel_addAF	Pathogenic	0.30	D
BayesDel_noAF	Pathogenic	0.20
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.50	T
Eigen	Pathogenic	0.70
Eigen_PC	Uncertain	0.66
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.95	D
M_CAP	Uncertain	0.12	D
MetaRNN	Pathogenic	0.81	D
MetaSVM	Uncertain	-0.11	T
MutationAssessor	Uncertain	2.9	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.50	T
PROVEAN	Pathogenic	-5.1	D
REVEL	Uncertain	0.36
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.022	D
Polyphen		1.0	D
Vest4		0.67
MutPred		0.46		Loss of MoRF binding (P = 2e-04);
MVP		0.53
MPC		0.24
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.48
gMVP		0.59

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs139327086; hg19: chr2-166731284;